The following U.S. Patents and Patent Applications are hereby incorporated by reference:
U.S. Pat. No. 5,425,431, issued on Jun. 20, 1995, to Brandt et al., entitled INTERLOCK CONTROL SYSTEM FOR POWER MACHINE, assigned to the same assignee as the present application; and
U.S. Pat. No. 5,187,993 issued on Feb. 23, 1993, to Nicholson et al.
U.S. Pat. No. 5,577,876, issued on Nov. 26, 1996, entitled xe2x80x9cHYDRAULIC INTERLOCK SYSTEMxe2x80x9d and assigned to the same assignee as the present application.
U.S. patent Ser. No. 09/495,729, filed Feb. 1, 2000, entitled IMPROVED ATTACHMENT CONTROL DEVICE.
The present invention deals with power machines. More specifically, the present invention deals with electronic controls of hydraulic cylinders on a skid steer loader.
Power machines, such as skid steer loaders, typically have a frame which supports a cab or operator compartment and a movable lift arm which, in turn, supports a work tool such as a bucket. The movable lift arm is pivotally coupled to the frame of the skid steer loader and is powered by power actuators which are commonly hydraulic cylinders. In addition, the tool is coupled to the lift arm and is powered by one or more additional power actuators which are also commonly hydraulic cylinders. An operator manipulating a skid steer loader raises and lowers the lift arm and manipulates the tool, by actuating the hydraulic cylinders coupled to the lift arm, and the hydraulic cylinder coupled to the tool. Manipulation of the lift arm and tool is typically accomplished through manual operation of foot pedals or hand controls which are attached by mechanical linkages to valves (or valve spools) which control operation of the hydraulic cylinders.
Skid steer loaders also commonly have an engine which drives a hydraulic pump. The hydraulic pump powers hydraulic traction motors which provide powered movement of the skid steer loader. The traction motors are commonly coupled to the wheels through a drive mechanism such as a chain drive. A pair of steering levers are typically provided in the operator compartment which are movable fore and aft to control the traction motors driving the sets of wheels on either side of the skid steer loader. By manipulating the steering levers, the operator can steer the skid steer loader and control the loader in forward and backward directions of travel.
It is also common for the steering levers in the operator compartment of the skid steer loader to have hand grips which support a plurality of buttons or actuable switches. The switches are actuable by the operator and are configured to perform certain functions. However, the hand grips simply contain, for example, actuable switches which are each wired to a main electronic controller or other circuit located remotely from the hand grip. This requires a fairly extensive wire harness or wiring assembly, to be incorporated into the hand grips during manufacturing. Also, different hand grips or wiring assemblies must often be used with different machine models because machine operation or functionality is slightly different or contains different options.
A control system controls actuation of a hydraulic cylinder on a skid steer loader. The control system includes movable elements, such as hand grips. The hand grips are intelligent in that each contains a microprocessor or other digital controller which monitors user actuable elements (such as switches, buttons, paddles, etc.). The controller sends a communication signal to a main control computer. The communication signal is indicative of the state of the user actuable elements and is, in one embodiment, a serial communication signal.